Various fixed and removable dental appliances have been employed in dentistry and orthodontics over the years.
Removable dental appliances have been used to treat conditions such as snoring, sleep apnea, bruxism, myofascial pain, and pain and inflammation associated with temporomandibular joint (TMJ) dysfunction. While several prior art appliances have been shown to be effective, they typically lack comfort thereby negatively impacting patient compliance. Patient compliance is key in any patient-driven treatment, since lack of compliance renders the treatment ineffective.
The act of positioning an acrylic splint, or biteguard, over the teeth of the upper or lower dentition has been shown to relax tense musculature. This is accomplished by the splint preventing the existing occlusion (bite) from controlling the jaw-to-jaw relationship at maximum intercuspation (Dawson (1989). Evaluation, Diagnosis, and Treatment of Occlusal Problems (2nd Ed). Saint Louis, Mo.: Mosby, pg. 184-190). Because all corrective tooth inclines are separated, permissive splints, or de-programmers, allow the muscles to function according to their own coordinated interactions, thus eliminating the cause and the effects of muscle incoordination. Any splint design is permissive if it unlocks occlusal incline contacts and provides a smooth gliding surface that permits uninhibited muscle positioning of the mandible. Separation of the posterior teeth substantially reduces the contractile strength and activity of the elevator muscles. Thus, the loading pressure against the joints is lessened.
Advancing the mandible can relieve pain associated with some types of TMJ dysfunction, including extracapsular TMJ pain. It is very common for patients with TMJ pain and discomfort to hold their lower jaw forward during the day and, in doing so, the mandibular condyles do not impinge on the tender retrodiscal tissues (as in retrodiscitis) or the inflamed capsular ligament (as in capsulitis). However, this conscious positioning of the jaw is lost during sleep. A removable dental appliance for opening the bite and/or advancing the mandible slightly, worn during sleep, can be quite effective in relieving extracapsular TMJ pain.
Bruxism is a condition characterized by parafunctional clenching and grinding of the teeth which can occur during wake or sleep. Bruxism causes wear and breakdown of the teeth (dentition) and the subject is generally unaware of their destructive behavior. For patients who suffer from bruxism, providing a splint over the upper and/or lower teeth protects the occlusal surfaces of the teeth from destructive forces generated during bruxing. Advancing the mandible slightly, as well as providing occlusal (bite) contact on the anterior segment of the appliance lessens the amount of force that can be generated by the bruxing patient, since forces are reduced when the posterior teeth are not engaged. Advancing the mandible slightly after opening the bite can further reduce clenching forces. Reduction in grinding and clenching can also relieve muscle pain and reduce the frequency and severity of headaches associated with bruxism.
Headache sufferers diagnosed with TMJ syndrome are typically treated with a jaw-repositioning appliance, designed to relieve pressure on the distressed temporomandibular joint and to allow a proper jaw-to-skull relationship. Typical of these are the orthotics or splints described in U.S. Pat. Nos. 4,671,766 and 4,519,386. The appliance covers the upper and/or lower posterior teeth and dictates jaw position by guiding the opposing jaw into the “normal” position. Unfortunately, the posterior teeth of the upper and lower jaws are approximated by way of the appliance, thus allowing the full force of the clenching to persist.
U.S. Pat. No. 5,085,584 discloses an intraoral discluding device for the prevention of tension, migraine headaches and TMJ syndrome caused by chronic clenching of the posterior mandibular and maxillary teeth by the temporalis muscle. The discluder is a small intraoral device having a dome-shaped tab supported by a conventional palatal arch attachment member which is retained by bent orthodontic wire. The device is inserted in the mouth and retained against the upper anterior teeth with the tab extending such that, as the mouth is closed, the tab comes into contact with the lower anterior incisal edges before the posterior teeth can touch each other. This renders the temporalis muscles ineffective, preventing high pressure clenching of the posterior teeth. This device does not provide a means of advancing the mandible.
Although it is well known that advancing the mandible can relieve TMJ pain and reduce bruxing, the concept of advancing the mandible to open the airway, such as to treat apnea or snoring, is relatively new to the field of dentistry.
Apnea is generally defined as a cessation of breathing, or airflow, lasting 10 seconds or more. Hypopnea generally refers to a 50% reduction in airflow for 10 seconds or more. Sleep apnea is classified as central, obstructive, or mixed apnea. In central sleep apnea, the respiratory, or chest, muscles make no attempt to breathe as a result of a CNS disorder, resulting in a loss of oxygen to the lungs. In obstructive sleep apnea (OSA), the respiratory muscles attempt to inspire but a blockage in the upper airway prevents air from reaching the lungs. In mixed apnea, the patient presents with a combination of these problems. It should be noted that oral appliance therapy typically cannot address central or mixed sleep apnea.
Upper airway resistance syndrome (UARS) is characterized by loud snoring that causes frequent awakening. An UARS patient has all the symptoms of OSA but without the apneic or hypopneic events. Snoring is generally caused by a relaxing of the pharyngeal musculature leading to restriction of the airway, causing vibration of the surrounding tissue upon the passage of air. The tongue as well as the soft palate are believed to be major causative factors in both snoring and obstructive sleep apnea.
When a subject is positioned in the supine position, the tongue falls to the back of the throat and blocks the airway. Moving the mandible forward widens the airway, thereby preventing or reducing snoring.
Sleep apnea is associated with an increased risk of hypertension and other cardiovascular and cerebrovascular diseases. Advancing the mandible has been shown to draw the tongue out of the airway, thereby opening the airway, to reduce episodes of snoring and obstructive sleep apnea. A recent epidemiological study of the general population reported that sleep breathing disorders, especially obstructive sleep apnea syndrome, are more prevalent in populations with tooth grinding (3.4 to 4.8%) than in those without (1.4%) (Kato et al. Bruxism and Orofacial Movements During Sleep. In, Attanasio and Bailey (eds.). Sleep Disorders: Dentistry's Role. Dental Clinics of North America, 45(4), 2001, p. 658). Severe occlusal wear (more than 20% of the clinical crowns) may indicate severe bruxism and complicate oral appliance therapy (Lowe. Oral Appliances for Sleep Breathing Disorders. In, Kryger, Roth and Dement (eds). Principles and Practice of Sleep Medicine (3rd Ed.). Philadelphia, Pa.: Saunders, 2001, pp. 930).
Various appliances for advancing the mandible have been developed over the years. Most of the two-piece appliances on the market today, i.e. appliances having both an upper and lower arch attachment member, serve to fix a patients jaw in the forward position during sleep. However, pain and discomfort result when the jaw is restricted from movement for extended periods of time. Many known two-piece appliances do not allow sufficient translational or sagittal jaw movement while the appliance is in place. Many also restrict vertical jaw movement. Discomfort reduces patient compliance, thereby reducing the overall effectiveness of the patient-driven treatment. Since patient compliance increases with the comfort and ease of using a dental appliance, there is a need to develop more comfortable dental appliances.
U.S. Pat. No. 5,427,117 discloses a dental device for preventing snoring and improving breathing, which includes an upper and lower arch attachment member of a deformable material in which a mold of the subject's upper and lower teeth is formed. A post extends from the upper arch attachment member and contacts the lower arch attachment member so that the lower jaw is extended forward, thereby reducing snoring. The device is designed to permit some movement of the lower jaw for improved comfort. In a particular embodiment, the forward location of the post, with respect to the user, is adjustable to allow titration of the degree of mandibular advancement. In a preferred embodiment, the upper and lower jaws are “locked” such that they cannot be opened more than a predetermined amount. Translational or lateral jaw movements are restricted as well. U.S. Pat. Nos. 5,365,945, 5,566,683, 6,305,376 and 6,845,774 describe similar devices.
In an attempt to offer improved comfort to the patient, a device called the SILENSOR™ snoreguard was developed, which creates tension between upper and lower arches to advance the mandible. The device consists of two transparent arch attachment members, or splints, one each for the upper and lower jaw. The lower jaw is held in a predetermined position by two connectors that are fixed laterally to the arch attachment members. The connector members are oriented in such a manner as to draw the jaw forward. The device permits limited movement of the lower jaw since the connector members offer a somewhat elastic property.
The above-mentioned appliances all require rigid mechanical components (i.e. hooks, wires, plastic fasteners, etc.) in order to produce advancement of the mandible. Mechanical components are subject to wear and destruction and can render an appliance bulky and cumbersome for a patient to wear. Furthermore, locking fasteners can snag the soft tissue in the oral cavity, including the tongue, causing discomfort and even lesions.
A magnetic dental appliance for treatment of snoring and sleep apnea was recently developed and studied in Sweden (Bernhold et al., Am J Orthod Dentofacial Orthop 1998; 113, 144-55). This device incorporates 8 magnets (2 in each posterior quadrant) in an “open field” configuration to advance the mandible. The magnets are embedded in an upper and lower acrylic arch attachment member in the posterior segment of each member. The magnets are positioned in both members such that the north poles of the magnets in one member attract the south poles of the magnets in the opposing member to urge the mandible forward. Strong magnetic attraction between the upper and lower sets of magnets essentially prevents jaw movement, which causes significant discomfort to the patient since the jaw muscles and TMJ are held in the same position for extended periods. The appliance is not titratable so no adjustability is permitted once the appliance is cast.
The use of magnets in the oral cavity is not an entirely new concept. Magnets have been used to fasten dentures to implant fixtures for a number of years now. The original systems employed the attractive forces between coated Alnico V magnets, implanted in the mandible, and magnets embedded in the dentures. These original systems met with little success due to insufficient holding power. Since the introduction of rare earth magnets in the 1970's to 1980's, such as samarium-cobalt and neodymium-iron-boron magnets, it has become possible to produce magnets with small enough dimensions for dental applications and yet still provide the necessary forces.
The first magnetic denture attachment devices were of the “open field” type, wherein two unshielded magnets are placed in the oral cavity in force-coupled relationship. Due to concerns about the possible harmful effects of “open field” magnetic forces on the local tissues, most magnetic denture systems are now of the “closed field” type. In this type of system, a soft magnetic or ferromagnetic material, such as ferritic or martensitic stainless steel or Pd—Co—Ni alloy, is implanted into the jaw, rather than a magnet, to provide attractive force to hold the denture in place. This implant is known as a “keeper”. In this configuration, the magnetic field lines are shunted through the keeper as it is the path of minimum energy and there is no magnetic field experienced in the oral cavity.
U.S. Pat. Nos. 6,659,771, 5,678,998, 5,013,243 and 6,299,450 describe small yet powerful magnets for cooperating with a non-magnet implanted “keeper” for denture attachment. The non-magnet keeper is made of a magnet-attracted material, such as a soft magnetic or ferromagnetic material, but is not a permanent magnet.
Magnets have been employed in aspects of orthodontics and dentistry other than denture attachments. U.S. Pat. No. 4,396,373 describes a removable orthodontic appliance for intruding one or more teeth. The appliance includes two rigid caps having internal shapes conforming to the crown portions of juxtaposed molars in the maxilla and mandible, respectively. The caps are adapted to be removably secured to said teeth. Two permanent magnets carried by the two caps, respectively, having facing poles which are in registry when the mouth is normally closed, exert a magnetic force in a direction substantially normal to the occlusal plane. The opposing magnets have confronting poles with like-polarity such that the magnets repel and develop intrusive forces upon the respective teeth.
U.S. Pat. No. 4,671,767 discloses both fixed and removable orthodontic devices that use magnets to correct Class II malocclusions. The magnets are secured to removable or fixed orthodontic devices and are positioned bilaterally in the posterior molar regions. The faces of the magnets are oriented such that they repel each other, thereby creating magnetic forces parallel to the occlusal plane for urging the mandible forward. Correction of Class II malocclusions involves, among other things, acting upon the mandible to urge it anteriorly until the jaw muscles adapt and, if possible, until regrowth of the condyle into the glenoid fossa occurs. Alignment of the teeth may be corrected in the process.
The magnetic orthodontic devices described above employ “open field” magnetic configurations, which are potentially harmful to the local tissues in the oral cavity, especially since the devices are designed for long-term use. Furthermore, the appliances are uncomfortable to wear.
Biological safety testing of magnets containing rare earth elements has evaluated both the effects of the static magnetic field and possible toxic effects of the materials or their corrosion products. These studies have demonstrated negligible cytotoxic effects of the magnetic field. However, it is of paramount importance to prevent corrosion from occurring. A clinical, histological, and immunohistochemical study, found no adverse long term effects on human buccal mucosa which had been in contact with acrylic-coated neodymium iron boron magnets and subject to the static magnetic field (Bondmark et al. Long-term effects of orthodontic magnets on human buccal mucosa: a clinical, histological and immunohistochemical study. European Journal of Orthodontics 1998; 20, 211-218). The evidence currently available from biological safety testing would suggest that the risk of harmful biological effects are negligible (Noar and Evans. Rare Earth Magnets in Orthodontics: An Overview. British Journal of Orthodontics 1999; 26(1), 29-37).
A subgroup of patients using oral appliance therapy, particularly those who suffer from sleep bruxism, experience considerable jaw discomfort the morning after wearing a rigid, single jaw position, oral appliance. A need to develop oral appliances that could allow for lateral jaw movement, as well as some degree of vertical jaw opening, was identified (Lowe. Oral Appliances for Sleep Breathing Disorders. Kryger, Roth and Dement (eds). Principles and Practice of Sleep Medicine (3rd Ed.). Philadelphia, Pa.: W B Saunders, 2001, pp 931).
It is desirable to provide an improved removable dental appliance for treatment of conditions such as snoring, obstructive sleep apnea, bruxism, myofascial pain and TMJ syndrome, that is simple and durable in construction and, most importantly, comfortable and safe for the patient. Comfort is an important factor in any patient-directed treatment where compliance is key.